Cleft palate speech is usually characterized by two major distortions, one of resonance and the other of articulation. Both relate to an inability to attain adequate velopharyngeal closure. The articulation errors associated with velopharyngeal inadequacy are of particular interest to clinician. and researchers because the problems they pose usually remain after surgical repair and the reasons they appear may have important implications for speech-motor control. It is paradoxical that, although velopharyngeal inadequacy stimulates compensatory speech behaviors, such responses tend to further undermine, rather than enhance, speech performance. The intriguing question of why individuals develop &nd maintain such detrimental behaviors has been the focus of our laboratory's attention over the past 30 years. Our studies suggest that these behaviors may be attempts to satisfy requirements of a regulating system. The hypothesis that speech aerodynamics follow the rules of a physiologic regulation system implies that the brain receives information, processes it and then directs the control activities. Implicit in this hypothesis are 1) the existence of sensors within the vocal tract that monitor the aerodynamic environment and 2) the capability for such afferent information to be used on-line to invoke appropriate motor responses. The primary objective of this current proposal is to assess the properties of the sensory system that may be used to monitor speech aerodynamics. The approach will involve physiologic and psychophysical assessments of the sensitivity of the monitoring system during speech. Specifically, we will use newly developed instrumentation that can alter resistance within the vocal tract environment in about 10 ms. These sudden changes in airway resistance during production of speech sounds will be used to assess the sensitivity of the monitoring system both physiologically and perceptually. Comparisons will be made between physiologic detection and psychophysical detection. This approach will also provide information on the responsivity of the aerodynamic monitoring system (e.e. latency of response) in noncleft subjects and subjects with velopharyngeal inadequacy. The information obtained from these experiments should prove to be helpful in elucidating the possible role of afferent information in the control of movements of speech structures and in the perception of changes within the vocal tract environment.